allegro_hand_ros

Allegro Hand ROS

This is the official release to control Allegro Hand with ROS Kinetic. Mostly, it is based on the old release of Allegro Hand ros package and the interfaces and controllers have been improved and rewritten much by Felix Duballet from EPFL. Thank you for the contribution.

You can find old release of the [hand ros package][1]. [1]: https://github.com/simlabrobotics/allegro_hand_ros_v4

It improves significantly upon the old release, simplifies the launch file structure, updates the package/node names to have a more consistent structure, improves the build process by creating a common driver, introduces an AllegroNode C++ class that reduces the amount of duplicated code. It also provides a python library that can control the hand directly.

It also provides the BHand library directly in this package (including both 32-bit and 64-bit versions, though 32-bit systems will need to update the symlink manually).

At this point no effort has been made to be backwards compatible. Some of the non-compatible changes between the two version are:

• Put all of the controllers into one package (allegro_hand_controllers) and made each controller a different node (allegro_node_XXXX): grasp, pd, velsat, and sim.
• Single launch file with arguments instead of multiple launch files with repeated code.
• Both the parameter and description files are now ROS packages, so that rospack find works with them.
• These packages will likely not work with pre-hydro versions (only tested on ROS Kinetic so far, please let me know if this works on other distributions).
• Added a torque controller (from @nisommer).
• Added a 'simulated' pass-through hand controller that sets the joint state to the desired joint state.

Launch file instructions:

There is now a single file, allegro_hand.launch that starts the hand. It takes many arguments, but at a minimum you must specify the handedness:

roslaunch allegro_hand_controllers allegro_hand.launch HAND:=right

Optional (recommended) arguments:

      NUM:=0|1|...
      ZEROS:=/path/to/zeros_file.yaml
      CONTROLLER:=grasp|pd|velsat|torque|sim
      RESPAWN:=true|false   Respawn controller if it dies.
      KEYBOARD:=true|false  (default is true)
      AUTO_CAN:=true|false  (default is true)
      CAN_DEVICE:=/dev/pcanusb1 | /dev/pcanusbNNN  (ls -l /dev/pcan* to see open CAN devices)
      VISUALIZE:=true|false  (Launch rviz)
      JSP_GUI:=true|false  (show the joint_state_publisher for *desired* joint angles)

Note on AUTO_CAN: There is a nice script detect_pcan.py which automatically finds an open /dev/pcanusb file. If instead you specify the can device manually (CAN_DEVICE:=/dev/pcanusbN), make sure you also specify AUTO_CAN:=false. Obviously, automatic detection cannot work with two hands.

The second launch file is for visualization, it is included in allegro_hand.launch if VISUALIZE:=true. Otherwise, it can be useful to run it separately (with VISUALIZE:=false), for example if you want to start rviz separately (and keep it running):

roslaunch allegro_hand_controllers allegro_viz.launch HAND:=right

Note that you should also specify the hand NUM parameter in the viz launch if the hand number is not zero.

Packages

• allegro_hand A python client that enables direct control of the hand in python code.
• allegro_hand_driver Driver for talking with the allegro hand.
• allegro_hand_controllers Different nodes that actually control the hand. The AllegroNode class handles all the generic driver comms, each class then implements computeDesiredTorque differently (and can have various topic subscribers):
  • grasp: Apply various pre-defined grasps, including gravity compensation.
  • pd: Joint space control: save and hold positions.
  • velsat: velocity saturation joint space control (supposedly experimental)
  • torque: Direct torque control.
  • sim: Just pass desired joint states through as current joint states.
• allegro_hand_description xacro descriptions for the kinematics of the hand, rviz configuration and meshes.
• allegro_hand_keyboard Node that sends the commanded grasps. All commands are available with the grasp controller, only some are available with the other controllers.
• allegro_hand_parameters All necessary parameters for loading the hand:
  • gains_pd.yaml: Controller gains for PD controller.
  • gains_velSat.yaml: Controller gains and parameters for velocity saturation controller.
  • initial_position.yaml: Home position for the hand.
  • zero.yaml: Offset and servo directions for each of the 16 joints, and some meta information about the hand.
  • zero_files/ Zero files for all hands.
• bhand Library files for the predefined grasps, available in 32 and 64 bit versions. 64 bit by default, update symlink for 32 bit.

Note on polling (from Wonik Robotics): The preferred sampling method is utilizing the Hand's own real time clock running @ 333Hz by polling the CAN communication (polling = true, default). In fact, ROS's interrupt/sleep combination might cause instability in CAN communication resulting unstable hand motions.

Useful Links

• Allegro Hand wiki.
• ROS wiki for original package.

Controlling More Than One Hand

When running more than one hand using ROS, you must specify the number of the hand when launching.

roslaunch allegro_hand.launch HAND:=right ZEROS:=parameters/zero0.yaml NUM:=0 CAN_DEVICE:=/dev/pcan0 AUTO_CAN:=false

roslaunch allegro_hand.launch HAND:=left  ZEROS:=parameters/zero1.yaml NUM:=1 CAN_DEVICE:=/dev/pcan1 AUTO_CAN:=false

Known Issues:

While all parameters defining the hand's motor/encoder directions and offsets fall under the enumerated "allegroHand_#" namespaces, the parameter "robot_description" defining the kinematic structure and joint limits remains global. When launching a second hand, this parameter is overwritten. I have yet to find a way to have a separate enumerated "robot_decription" parameter for each hand. If you have any info on this, please advise.

Installing the PCAN driver

Before using the hand, you must install the pcan drivers. This assumes you have a peak-systems pcan to usb adapter.

1. Install these packages

   sudo apt-get install libpopt-dev ros-kinetic-libpcan

2. Download latest drivers: http://www.peak-system.com/fileadmin/media/linux/index.htm#download

Install the drivers:

make clean; make NET=NO_NETDEV_SUPPORT
sudo make install
sudo /sbin/modprobe pcan

Test that the interface is installed properly with:

 cat /proc/pcan

You should see some stuff streaming.

When the hand is connected, you should see pcanusb0 or pcanusb1 in the list of available interfaces:

ls -l /dev/pcan*

If you do not see any available files, you may need to run:

sudo ./driver/pcan_make_devices 2

from the downloaded pcan folder: this theoretically creates the devices files if the system has not done it automatically.

3. Build the sources

   catkin_make source devel/setup.bash

4. quick start cd src/allegro_hand_controllers/launch roslaunch allegro_hand.launch HAND:=right